The nuclear cluster of the Milky Way: Our primary testbed for the interaction of a dense star cluster with a massive black hole

TL;DR

This paper reviews the properties, structure, and dynamics of the Milky Way's nuclear star cluster, highlighting its significance as a primary observational testbed for studying dense star clusters interacting with a central massive black hole.

Contribution

It provides a comprehensive observational overview of the MWNSC, emphasizing its role in understanding stellar dynamics near supermassive black holes and comparing it with extragalactic nuclear clusters.

Findings

MWNSC is a typical nuclear star cluster with dense, massive stellar populations.

The cluster's properties are crucial for studying stellar dynamics and black hole interactions.

Data from the MWNSC allows analysis of star orbits at milli-parsec scales.

Abstract

This article intends to provide a concise overview, from an observational point-of-view, of the current state of our knowledge of the most relevant properties of the Milky Way's nuclear star cluster (MWNSC). The MWNSC appears to be a typical specimen of nuclear star clusters, which are found at the centers of the majority of all types of galaxies. Nuclear clusters represent the densest and most massive stellar systems in the present-day Universe and frequently coexist with central massive black holes. They are therefore of prime interest for studying stellar dynamics and the MWNSC is the only one that allows us to obtain data on milli-parsec scales. After discussing the main observational constraints, we start with a description of the overall structure and kinematics of the MWNSC, then focus on a comparison to extragalactic systems, summarize the properties of the young, massive stars in the immediate environment of the Milky Way's central black hole, Sagittarius\,A*, and finally focus on the dynamics of stars orbiting the black hole at distances of a few to a few tens of milli parsecs.